Is this what you are talking about
https://www.amazon.com/EATON-419GY-125-Volt-Grounding-Adapter/dp/B000H5QZ9S/ref=asc_df_B000H5QZ9S/?tag=hyprod-20&linkCode=df0&hvadid=193994910693&hvpos=&hvnetw=g&hvrand=7822169822213890949&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9017024&hvtargid=pla-309396144231&psc=1
Old ones Like 1960 old the two prongs were the same size.. Old 2 slot outlets often the same.. Modern ones the "neutral" side is wider and won't go into a non-polarized outlet This is a safety thing.
Dremel will "Modify" the neutral blade if you need to do it.